This invention relates to downhole drilling assemblies, specifically downhole drilling assemblies for use in oil, gas, geothermal, and horizontal drilling. The ability to efficiently provide a power source downhole is desirable to electronically and mechanically power downhole instrumentation.
U.S. Pat. No. 4,802,150 to Russell et al., which is herein incorporated by reference for all that it contains, discloses a downhole signal generator for a mud-pulse telemetry system that comprises a flow constrictor defining a throttle orifice for the mud passing along a drill string, a throttling member displaceable with respect to the throttle orifice to modulate the mud pressure for the purpose of transmitting measurement data up the drill string, and a turbogenerator. The turbogenerator incorporates an annular impeller surrounding a casing and arranged to be driven by the mud passing along the drill string, and a rotatable magnet assembly disposed in a mud-free environment within the casing. The impeller includes an electrically conductive drive ring and the rotatable magnet assembly includes rare earth magnets, so that, when the impeller is rotated by the mud flow, eddy currents are induced in the drive ring by the magnetic field associated with the magnets and the magnet assembly is caused to rotate with the impeller by virtue of the interaction between the magnetic field associated with the induced currents. In this manner torque may be imparted to an electrical generator within the casing without a rotating seal having to be provided between the impeller and the generator.
U.S. Pat. No. 6,011,334 to Roland, which is herein incorporated by reference for all that it contains, discloses an electric power generator driven by a fluid circulating under pressure in a pipe includes an internal moving contact placed inside a non-magnetic section of the pipe, and a stator placed around the pipe. The internal moving contact includes permanent magnets, a rotational drive means, and means of support. The electric power generator does not require any sealed joints for the passage of mechanical shafts or electric cables and is particularly adapted for the production of electricity from dangerous fluids which circulate in pipes under high pressure. The electric power generator has an application in gas and liquid transport networks, particularly at isolated hydrocarbon production sites.